Focusing issue in cold weather???

[Mark Theriot]

Anyone ever have an issue (inaccurate focus) in very cold weather?

i had an issue this morning that is baffling me. Good morning light and nothing was in focus as distances increased. Looking through the lens, I seemed to notice "wavy lines" like you'd see in the summer coming off of really hot asphalt. Like "heat haze".

I've had this issue before, shooting out of a car with the heater on - rolling the window down on a very cold day. Focus was off due to the temperature waves rolling out of the car - but never away from the car.

Am I crazy, or could I have had a similar issue in very cold weather. Early morning temps were 0 degrees and it was around 10 degrees and bright warm sunshine when I was shooting.

i tried shooting off a locked down tripod in manual mode and live view - at the best focus point, all I had was a fuzzy image. The last thing I want to do is blame it on equipment.

Thanks!
Mark

[arash_hazeghi]

Mark this is due to heat refraction. ( when there are pockets of air that are cooler or warmer ) it happens in both hot and cold days. It is normal and has nothing to do with focus.

[Mark Theriot]

Great, thanks Arash. It killed the whole morning's shoot.

Mark

[John Chardine]

Hi Mark- It's a big issue and I come across it fairly often. I'm in Florida right now and we has 32°F/0°C this AM. I was out early and the air was very bad as the sun came up.

Air shimmer like this prevents your auto-focus from performing accurately as it should. With heat shimmer you will usually hear the AF (set to AI-Servo) "hunting" as the shimmer changes what the AF sensor is seeing.

The only way to salvage the day in these conditions is to (if possible) shoot close to your subject to minimise the amount of air between the lens and the subject.

[Mark Theriot]

Appreciate it John, thanks!

[Charles Glatzer]

The more inclement the weather and/or atmospheric conditions the shorter the focal length and closer to the subject you need to shoot.